JP5200323B2 - High frequency semiconductor device - Google Patents

Description

  The present invention relates to a high frequency semiconductor device, and more particularly to a field effect type high frequency semiconductor device used as a power amplifier in a high frequency band of 3 GHz or more.

Solid state power amplifiers (SSPA) are widely used in wireless communication systems such as satellite communications and terrestrial microwave links. Conventionally, a field effect transistor using GaAs has been used as an SSPA transistor of 3 GHz or more. In recent years, broadbandization of communication has progressed, and it is increasingly required to transmit a large amount of information. In order to increase the amount of information transmitted in response to such a request, it is necessary to increase the transmission speed, and the demand for SSPA used in a higher frequency band increases, resulting in high gain and efficiency. There is a need for high-power transistors.
For example, a p-HEMT is used as an internal adjustment type high-frequency high-power FET in response to such a requirement (hereinafter, n-conductivity type is “n-”, p-conductivity type is “p-”, and particularly impurities). (Indicates “i-” for those not injected). Conventional p-HEMTs have been improved in performance as low-noise amplification transistors, but recently, field effect transistors with high breakdown voltage and high output have been developed as power amplifiers.

  As a well-known example of such a field effect transistor, in order to reduce the size of the HEMT element, the gate electrode is patterned so as to be a continuous line in the chip region, and between the source electrode and the drain electrode. Shows an example of patterning so as to extend in the vertical direction on the paper surface and to extend in the left-right direction in other portions (see, for example, Patent Document 1, [0022] and FIG. 8).

  As another known example, a discontinuous cap layer is provided between the gate electrode and the drain electrode of the HEMT in order to achieve both high breakdown voltage and good high frequency characteristics in a compound semiconductor field effect transistor for high frequency. Examples provided are disclosed (for example, see Patent Document 2, [0003], [0009], [0010] and FIGS. 3 and 4).

  As another known example, in a field effect transistor, a gate electrode is provided on a side surface of a recess, a source electrode is provided on a flat portion of the substrate in the vicinity of the recess where the gate electrode is formed, and a drain electrode is formed on the bottom of the recess. Thus, the distance from the source electrode side edge of the recess to the source electrode does not change, but since the gate electrode is formed close to the source electrode, the source parasitic resistance is greatly reduced, and the electric field in the channel directly under the gate electrode is reduced. An example is disclosed in which the horizontal component is reduced and is relaxed by the vertical component up to the bottom of the recess, so that the gate-drain breakdown voltage is improved (see, for example, Patent Document 3, [0016], [0017], and FIG. 1). ).

  As another known example, in a T-type gate structure, a description of a structure in which a recess width between a gate and a source, which is called an offset gate structure, is different, and a T-electrode on the drain side is formed by forming an asymmetric T-type electrode. The gate-drain breakdown voltage can be reduced by reducing the parasitic capacitance generated at the bottom of the mold electrode compared to that on the source side, or by forming the source side recess etching in one step and the drain side recess etching shape in two steps. There is a description that it can be improved (see, for example, Patent Document 4, [0008], [0030], [0033] and FIGS. 1 and 3).

  In another known example, a specific device of a high output p-HEMT having an offset gate structure having a T-type gate is disclosed (for example, Non-Patent Document 1).

JP 2005-159157 A JP 2001-60684 A JP-A-5-129344 JP 2000-21900 A H. Amasuga et al., “A High Power Density TaN / Au T-gate pHEMT with High Humidity Resistance for Ka-Band Applications,” IEEE IMS2005 Digest, June 2005

In such a field effect transistor, generally, when the gate-drain distance Lrd is long, the electric field between the gate and the drain is relaxed, so that the gate-drain breakdown voltage Vgd0 is increased. However, at a high frequency of about 14 GHz, the output power of the field effect transistor including the p-HEMT decreases.
For example, when a p-HEMT having a different Lrd at 14 GHz is loaded and pulled, that is, the output impedance is changed and the output power P1 dB (W / mm) is measured, when Lrd = 0.45 μm, P1 dB≈0.78 W / mm When Lrd = 2.05 μm, P1 dB≈0.25 W / mm. In addition, between Lrd = 0.45 μm and Lrd = 2.05 μm, the measurement was performed with the increment of Lrd being 0.4 μm, and the increase in Lrd between Lrd = 0.45 μm and Lrd = 2.05 μm As a result, P1 dB is almost linearly reduced.
The parasitic resistance Rd of the drain slightly increases due to the increase in Lrd, but the output power described above rapidly decreases more than the increment of Rd.
In particular, a decrease in output power due to an increase in the gate-drain distance Lrd is slight at a relatively low frequency such as 1 GHz, but is significantly reduced as the frequency is increased.
In order to prevent this, the gate-drain distance Lrd may be shortened. In this case, however, the gate-drain breakdown voltage Vgd0 is lowered, the high voltage cannot be operated, and the output power does not increase. was there.

  The present invention has been made to solve the above problems, and a first object is to construct a high-frequency semiconductor device capable of increasing output power without lowering the gate-drain breakdown voltage.

A high-frequency semiconductor device according to the present invention includes a semi-insulating semiconductor substrate, an n-type first electron supply layer disposed on the semiconductor substrate, and sequentially disposed on the semiconductor substrate, an undoped channel layer, An active region including an n-type second electron supply layer and an undoped Schottky layer ; a gate electrode disposed on the surface of the Schottky layer in the active region; and a leg portion of the gate electrode embedded in the surface of the Schottky layer An undoped cap layer disposed on the surface of the cap layer, and a source electrode and a drain electrode disposed on the surface of the cap layer so as to face each other with the gate electrode interposed therebetween. the first region is disposed wider toward the drain electrode from the gate electrode, the distance is long is disposed than the distance between the gate electrode and the source electrode of the gate electrode and the drain electrode between Those were.

  In the high-frequency semiconductor device according to the present invention, since the first region between the gate electrode and the drain electrode is disposed wide from the gate electrode toward the drain electrode, the width of the drain electrode in the first region Even if the maximum current increases in proportion to the first region and a pseudo FET is generated in the first region, a large current is supplied to the FET constituted by the gate electrode, so that a decrease in output power can be suppressed. it can.

Embodiment 1 FIG.
FIG. 1 is a plan view of a high-frequency semiconductor device according to an embodiment of the present invention. 2 is a cross-sectional view of the high-frequency semiconductor device taken along the line II-II in FIG. In the following drawings, the same reference numerals represent the same or equivalent ones.
In FIG. 1, a p-HEMT 10 as a high-frequency semiconductor element used in a high-frequency semiconductor device is used as a power amplifier as a solid-state amplifier in a wireless communication system such as satellite communication or terrestrial microwave line. This p-HEMT 10 is an internal matching type high frequency high power FET, and is an element mainly used at 14 GHz or more and having an output of 0.5 W or more per 1 mm of gate width. Here, the internal matching type means that an internal matching substrate is provided outside the high-frequency semiconductor element in the package.
In FIG. 1 and FIG. 2, the p-HEMT 10 includes an inactive region 14 surrounding the element region 12.

In the element region 12, a gate electrode 18 is disposed on an active region 16 including a channel layer 30 (described in FIG. 2), and a source electrode 20 and a drain electrode 22 are sandwiched between the gate electrode 18 on the active region 16. They are arranged opposite to each other.
In FIG. 1, the contact layer 38 shown in FIG. 2 is omitted, and the upper portion of the T-type electrode of the gate electrode 18 is omitted, and the T-type leg portion joined to the active region 16 is omitted. Only the lower layer is displayed. This display method is the same in the following plan views.
In FIG. 1, the gate width of the gate electrode 18 is the length in the y direction, and the gate length Lg is the length in the x direction.
The active region between the gate electrode 18 and the drain electrode 22 is a drain side active region 16a as a first region, and the active region between the gate electrode 18 and the source electrode 20 is a source side active region 16b.

In general, when the gate-drain distance Lrd is long, the electric field between the gate and drain is relaxed, so that the gate-drain breakdown voltage Vgd0 is increased. For example, in the p-HEMT 10, the gate-drain distance Lrd is about 0.1 μm to several tens of μm. The sum of the drain side active region 16a and the source side active region 16b is about 0.3 μm to several tens of μm.
In the p-HEMT 10, for example, the gate length Lg is about 0.3 μm and the gate width is about 60 μm.
In the p-HEMT 10, the distance between the gate electrode 18 and the source electrode 20 is reduced, and the distance Lrd between the gate electrode 18 and the drain electrode 22 is made larger than the distance between the gate electrode 18 and the source electrode 20. Thus, the gate-drain breakdown voltage Vgd0 is increased while reducing the source resistance.
Further, in this embodiment, the width (the length in the y direction) of the source side active region 16b is the same as the electrode width of the gate electrode 18 and the source electrode 20, but the width of the drain side active region 16a (the y direction). The length of the gate electrode 18 continuously increases from the electrode width of the gate electrode 18 to the width of the drain electrode 22 as it approaches the drain electrode 22 from the gate electrode 18.

In FIG. 2, a stacked structure of the p-HEMT 10 is shown.
The p-HEMT 10 includes a semi-insulating GaAs substrate 24 as a semiconductor substrate, a buffer layer 26, a lower electron supply layer 28 formed of n-AlGaAs, a channel layer 30 formed of i-InGaAs, n− An upper electron supply layer 32 made of AlGaAs and a Schottky layer 34 made of i-AlGaAs are sequentially arranged, and a T-type gate electrode 18 is Schottky bonded to the surface of the Schottky layer 34.
Further, a cap layer 36 made of i-GaAs is disposed on the surface of the Schottky layer 34 so as to embed the lower leg portion of the gate electrode subjected to Schottky junction.
Contact layers 38 made of n-GaAs are disposed on the source region and the drain region on the surface of the cap layer 36, respectively, and the source electrode 20 and the drain electrode 22 are disposed on the contact layer 38. A double hetero p-HEMT device is formed.
Then, leaving the element region 12 and injecting proton (H) or helium (He) to the depth of the GaAs substrate 24 around the element region 12, an inactive region 14 is formed, and element isolation is performed.

The thickness and impurity concentration of each of these layers are, for example, that the lower electron supply layer 28 and the upper electron supply layer 32 have a thickness of 500 mm, the n-AlGaAs impurity concentration is 1 × 10 ¹⁸ cm ⁻³ , and the channel layer 30 layer. The thickness is 30 to 500 mm, the Schottky layer 34 is 50 to 500 mm, the cap layer 36 is 200 to 2000 mm, the contact layer 38 is 500 to 2000 mm, and the n-GaAs impurity concentration is 1 × 10. It is formed to about ¹⁸ cm ⁻³ .
Among these layers, the active region 16 that is an active semiconductor region is composed of the lower electron supply layer 28, the channel layer 30, the upper electron supply layer 32, and the Schottky layer 34 in this embodiment. is there. In the active region 16, a channel is formed in the channel layer 30 at the interface between the lower electron supply layer 28 and the channel layer 30 and in the channel layer 30 at the interface between the upper electron supply layer 32 and the channel layer 30. Transistors operate as holes flow.
In the p-HEMT 10, an original field effect transistor formed immediately below the gate electrode 18 is a first FET. When the gate-drain distance Lrd is increased in order to increase the gate-drain breakdown voltage Vgd0 as in the p-HEMT 10, the gate-drain drain-side active region 16a has no gate electrode, but the gate Since a channel similar to that directly below the electrode 18 exists, if charges are trapped (trapped) in or on the surface of the cap layer 36, a pseudo like that shown in FIG. 2A in addition to the first FET is obtained. A field effect transistor and a second FET are configured.

FIG. 3 is an equivalent circuit of a p-HEMT considering a pseudo FET of a high-frequency semiconductor device according to an embodiment of the present invention.
In FIG. 3, the gate of the first FET 40 is connected to the gate electrode 18, the source is grounded via the source electrode 20, and the drain electrode is connected to the drain electrode 22 via a circuit formed by the second FET 42 and resistors R1 and R2. Has been.
Since the second FET 42 is not normally depleted, it is considered to be an ON-state FET, and only a small resistance is added between the gate and the drain. However, in high power operation at a high frequency such as 14 GHz, a current that greatly exceeds the DC maximum current Imax flows due to the parasitic capacitance associated with the first FET 40.
At this time, if the width of the active region between the gate and the drain is equal to the width of the active region between the gate and the source, the second FET 42 cannot supply a current exceeding Imax and the resistance increases. However, the current that flows was suppressed, and for this reason, the phenomenon that the output power did not increase occurred.
However, in the p-HEMT 10, the electrode width (length in the y direction) of the drain electrode 22 is made longer than the gate width of the gate electrode 18 and the width of the source side active region 16b (length in the y direction). The width of the region 16a (the length in the y direction) is continuously expanded from the electrode width of the gate electrode 18 to the width of the drain electrode 22 from the gate electrode 18 toward the drain electrode 22.

Since the layer structure of the active region 16 is the same in both the drain-side active region 16a and the source-side active region 16b, the maximum current increases in proportion to the width of the active region 16 (the length in the y direction). Therefore, the second FET 42 configured in the drain side active region 16a can supply a larger current than the first FET 40. Therefore, even in a large power operation at a high frequency such as 14 GHz, a large current can be supplied to the first FET 40 without increasing the resistance of the second FET 42, so that a decrease in output power is suppressed.
That is, in the p-HEMT 10, a decrease in output power can be suppressed without reducing the gate-drain distance Lrd. Therefore, a larger output power can be obtained without lowering the gate-drain breakdown voltage Vgd0.

FIG. 4 is a plan view showing a modification of the high-frequency semiconductor device according to one embodiment of the present invention.
FIG. 1 shows an example of one element, but the high-frequency semiconductor element of FIG. 4 is an example having a plurality of p-HEMT elements. In order to increase the normal output power, a plurality of p-HEMT elements are continuously arranged.
In the p-HEMT 46, the source electrode 20 or the drain electrode 22 of the elements of the two p-HEMTs 10 are arranged to be shared, the source-side active region 16b is set with the source electrode 20 as the axis of symmetry, and the drain electrode 22 is set as the axis of symmetry. As a result, a plurality of p-HEMT 10 elements are continuously arranged.
Further, even in the case of the p-HEMT 46, the distance between the gate electrode 18 and the source electrode 20 is reduced, and the distance Lrd between the gate electrode 18 and the drain electrode 22 is set larger than the distance between the gate electrode 18 and the source electrode 20. Thus, the gate-drain breakdown voltage Vgd0 is increased while reducing the source resistance.
Furthermore, the width (length in the y direction) of the source side active region 16b is the same as the electrode width of the gate electrode 18 and the source electrode 20, but the width (length in the y direction) of the drain side active region 16a is From the electrode 18 toward the drain electrode 22, the electrode width of the gate electrode 18 continuously increases from the width of the drain electrode 22.
Thus, the p-HEMT 46 constitutes a high-frequency semiconductor element having a desired output power by continuously arranging a plurality of elements of the p-HEMT 10.

  In the p-HEMT 10 and the p-HEMT 46, by increasing the gate-drain distance Lrd rather than the gate-source distance, the gate-drain breakdown voltage Vgd0 is increased while reducing the source resistance, and the width of the drain-side active region is increased. Is continuously increased from the gate electrode width to the drain electrode width from the gate electrode to the drain electrode, thereby suppressing a decrease in output power without decreasing the gate-drain breakdown voltage Vgd0. Can do. As a result, a high-frequency semiconductor device having a high breakdown voltage and a larger output power can be configured.

In the p-HEMT 10 and the p-HEMT 46, the width of the drain side active region 16a is continuously increased from the electrode width of the gate electrode 18 to the width of the drain electrode 22 from the gate electrode 18 toward the drain electrode 22. However, it may be expanded in stages.
As described above, in the high-frequency semiconductor device according to one embodiment of the present invention, an active device including a semi-insulating semiconductor substrate and a channel layer formed on the semiconductor substrate and made of a conductive semiconductor layer. A region, a gate electrode disposed on the active region, and a source electrode and a drain electrode disposed opposite to each other on the surface of the active region via the gate electrode, The first region between the gate electrode and the drain electrode is disposed wider from the gate electrode toward the drain electrode. With this configuration, the maximum current is proportional to the width of the drain electrode in the first region. Even if a pseudo FET is generated in the first region, a large current is supplied to the FET constituted by the gate electrode, so that a decrease in output power can be suppressed. As a result, a high-frequency semiconductor device having a high breakdown voltage and a larger output power can be configured.

  In addition, a plurality of source electrodes, gate electrodes, and drain electrodes are continuously arranged by sharing a source electrode or a drain electrode and arranging a gate electrode with these as symmetry axes, and a high frequency signal having a desired output power. A semiconductor element can be constituted.

Embodiment 2. FIG.
FIG. 5 is a plan view of a high-frequency semiconductor device according to one embodiment of the present invention. 6 is a cross-sectional view of the high-frequency semiconductor device taken along the line VI-VI in FIG. The cross-sectional view of the high-frequency semiconductor element in the VV cross section of FIG. 5 is the same as FIG.
As shown in FIG. 5, in the p-HEMT 50 according to the second embodiment, the active region 16 is divided into two portions by an inactive region 52 extending between the source electrode 20 and the drain electrode 22. The individual source side active regions 16b1 and 16b2 extend in the x direction with a uniform width (length in the y direction) between the gate electrode 18 and the source electrode 20, but the individual drain side active regions The widths (length in the y direction) of 16a1 and 16a2 are continuously expanded from the electrode widths of the individual gate electrodes 181 and 182 from the gate electrode 18 toward the drain electrode 22.

As shown in FIG. 2 which shows a cross-sectional view of the high-frequency semiconductor element in the VV cross section of FIG. 5, the stacked structure of the p-HEMT 50 is the same as that of the p-HEMT 10 according to the first embodiment. Further, in this embodiment shown in FIG. 6, the inactive region 52 is formed by injecting proton (H) or helium (He) from the cap layer 36 to the depth of the GaAs substrate 24, and the active region 16 is divided. It has been broken.
Considering the case where the gate width is, for example, 200 μm, the width of the drain-side active region 16a is from the gate electrode 18 toward the drain electrode 22, and from the total electrode width of the gate electrode 18 to the total width of the drain electrode 22. When the ratio of the total width of the drain electrode 22 to the total electrode width of the gate electrode 18 is increased, current is supplied only to the vicinity of the edge of the width of the drain-side active region 16a. In some cases, it is difficult to supply current to the central portion of the width of 16a.
However, in the p-HEMT 50, the drain-side active region 16a is divided into, for example, two parts to form drain-side active regions 16a1 and 16a2. Therefore, the distance from each position immediately below the gate electrode 18 to the drain electrode 22 is Since a large difference does not occur, current is supplied almost uniformly to the drain side active region 16a, and a maximum operating current proportional to the width of the drain side active region 16a flows.
For this reason, in addition to the effect of p-HEMT10 of Embodiment 1, larger output power can be obtained efficiently. Although the active region 16 is divided into two in this embodiment, the number of divisions may be increased.

FIG. 7 is a plan view of a modified example of the high-frequency semiconductor device according to one embodiment of the present invention. Note that the cross-sectional view of the high-frequency semiconductor element in the section VIIa-VIIa in FIG. 7 is the same as FIG. Further, the cross-sectional view of the high-frequency semiconductor element in the section VIIb-VIIb in FIG. 7 is the same as FIG.
In FIG. 7, the p-HEMT 56 has basically the same structure as the p-HEMT 50. However, the edge in contact with the inactive region 14 and the edge in contact with the inactive region 52 in the drain side active region 16a are on the gate electrode 18 side. It expands stepwise from the drain electrode 22 toward the drain electrode 22. With this configuration, the width (length in the y direction) of each of the drain-side active regions 16a1 and 16a2 increases stepwise from the electrode width of each of the gate electrodes 181 and 182 from the gate electrode 18 toward the drain electrode 22. ing.
For example, the width (the length in the y direction) of the drain side active regions 16a1 and 16a2 of the p-HEMT 56 is expanded in two steps here. The width (the length in the y direction) of the drain-side active regions 16a1 and 16a2 of the p-HEMT 56 is expanded in two stages, but may be expanded in more stages.

In the p-HEMT 56 of this modification, the width (length in the y direction) of each drain-side active region 16a1 and 16a2 is increased from the gate electrode 18 toward the drain electrode 22 as in the p-HEMT 50. Compared with the case where the electrodes 181 and 182 are continuously expanded from the electrode width, the overhang portion 58 which is a region extending outside the drain-side active regions 16a1 and 16a2 is formed and the active region is widened so that the parasitic resistance is reduced. be able to.
Since the current flows through a low resistance area, the overhanging portion 58 that spreads to the outside works effectively, so that the maximum operating current can be increased and a larger output power can be obtained.
As described above, in the high-frequency semiconductor device according to one embodiment of the present invention, the first region of the active region is adjacent to a part of the gate electrode and extends in the gate length direction of the gate electrode. The active region is divided into a plurality of regions, and each of the divided regions is arranged wide from the gate electrode toward the drain electrode. Even when the gate width increases, the width of the first region is increased. Current is supplied evenly in the direction, and large output power can be obtained efficiently.

Embodiment 3 FIG.
FIG. 8 is a plan view of a high-frequency semiconductor device according to one embodiment of the present invention. The cross-sectional view of the high-frequency semiconductor element in the section VIIIa-VIIIa in FIG. 8 is the same as FIG. Further, the cross-sectional view of the high-frequency semiconductor element in the section VIIIb-VIIIb in FIG. 8 is the same as FIG.
In FIG. 8, the p-HEMT 60 has a structure basically similar to that of the p-HEMT 56. However, in the p-HEMT 60, the width (length in the y direction) of the drain side active regions 16a1 and 16a2 is, for example, two levels. In addition, the shapes of the p-HEMT 56 and the drain electrode 22 are different. That is, the drain electrode 22 facing the gate electrode 18 has a concave shape as a whole toward the gate electrode 18 as the drain side active region 16a. That is, the drain electrode 22 has a concave shape having parallel straight portions facing and parallel to the gate electrode 18 and edges bent at right angles to the gate electrode 18 at both ends of the parallel straight portions.

For this reason, in the p-HEMT 60, the length of the edge of the drain electrode 22 in contact with the drain side active region 16a becomes longer. Accordingly, power can be supplied also from the lateral direction of the drain side active region 16a, and a larger current can be supplied.
The p-HEMT 60 is a case where the width (the length in the y direction) of the drain side active regions 16a1 and 16a2 is gradually increased. The drain electrode 22 may be concave toward the gate electrode 18 as a whole of the drain side active region 16a.
The p-HEMT 60 is a case where the drain side active region 16a is divided by the inactive region 52, but the width (length in the y direction) of the drain side active region 16a is the drain electrode 22 as in the p-HEMT 10. In the case where the width of the gate electrode 18 is continuously expanded from the width of the gate electrode 18 to the width of the drain electrode 22 without being divided by the inactive region as it approaches, the drain electrode 22 facing the gate electrode 18 is The drain side active region 16a as a whole may be concave toward the gate electrode 18.
FIG. 9 is a plan view of a modification of the high-frequency semiconductor device according to one embodiment of the present invention. Note that the cross-sectional view of the high-frequency semiconductor element in the section IXa-IXa in FIG. 9 is the same as FIG. Further, the cross-sectional view of the high-frequency semiconductor element in the section IXb-IXb in FIG. 9 is the same as FIG.

The p-HEMT 64 in FIG. 9 has basically the same structure as the p-HEMT 60, but the differences from the p-HEMT 60 are as follows.
That is, the drain electrode 22 of the p-HEMT 60 has a concave shape as a whole on the drain side active region 16a toward the gate electrode, whereas the drain electrode 22 of the p-HEMT 64 has a protruding portion at a portion facing the inactive region 52. 66, and the drain electrodes 22a and 22b have concave shapes corresponding to the respective drain side active regions 16a1 and 16a2 toward the gate electrode 18.
The individual edges of the drain electrodes 22a and 22b that face the gate electrodes 181 and 182 are parallel straight portions facing the gate electrodes 181 and 182 and both ends of the parallel straight portions toward the gate electrodes 181 and 182. Each edge is connected to the entire width direction of the drain electrode 22 through a protrusion 66.
For this reason, in the p-HEMT 64, the length of the edge of the drain electrode 22 in contact with the drain side active region 16a is longer, and current is supplied from the lateral direction individually for the drain side active regions 16a1 and 16a2. Can do. Therefore, a larger current can be supplied to each of the drain side active regions 16a1 and 16a2. As a result, the drain-side active region 16a as a whole can supply a larger current, so that a larger output power can be obtained.
In this modified example, one protrusion 66 is provided, but a number of protrusions may be provided opposite the inactive region 52.

FIG. 10 is a plan view of another modification of the high-frequency semiconductor device according to one embodiment of the present invention. Note that the cross-sectional view of the high-frequency semiconductor element in the Xa-Xa cross section of FIG. 10 is the same as FIG. Further, the cross-sectional view of the high-frequency semiconductor element in the Xb-Xb cross section of FIG. 10 is the same as FIG.
In the p-HEMT 70 in FIG. 10, the width (length in the y direction) of each drain-side active region 16a1 and 16a2 is from the electrode width of each gate electrode 181 and 182 from the gate electrode 18 toward the drain electrode 22. The point of continuous expansion is the same as that of the p-HEMT 50 of the second embodiment. The drain electrode 22 has a projection 66 at a portion facing the inactive region 52 and the drain electrode 22 is connected to the gate electrode 18. The p-HEMT 64 is the same as the p-HEMT 64 in that it has a concave shape corresponding to each of the drain side active regions 16a1 and 16a2.

However, the difference between the shape of the drain electrode 22 of the p-HEMT 70 and that of the p-HEMT 60 is as follows.
That is, in the p-HEMT 64, the individual edges of the drain electrodes 22a and 22b facing the gate electrodes 181 and 182 are parallel parallel portions facing the gate electrodes 181 and 182 and both ends of the parallel straight portions. The gate electrodes 181 and 182 have a shape composed of straight portions bent at right angles to the gate electrodes 181 and 182, and individual edges of the gate electrodes 181 and 182 are connected to the drain electrode 22 in the full width direction via the protrusions 66. On the other hand, in the p-HEMT 70, the individual edges of the drain electrodes 22a and 22b that face the gate electrodes 181 and 182 are parallel to the parallel straight portions 221 that face and face the gate electrodes 181 and 182 in parallel. An arc 222 having a radius from the gate electrode 181 or 182 connected at both ends of the straight line portion 221 to the parallel straight line portion 221 has a radius, and each edge has a full width of the drain electrode 22 via the protrusion 66. Connected in the direction.
With this configuration, in the p-HEMT 70, the distances from the positions immediately below the gate electrodes 181 and 182 to the drain electrodes 22a and 22b are constant, and the distance between the gate and drain electrodes is uniform. Therefore, current is supplied uniformly from the drain electrode 22 and the breakdown voltage Vgd0 is also uniform in the active region 16. Therefore, a current is evenly supplied in the active region 16, a maximum operating current proportional to the width of the active region 16 can be obtained, and a larger output power can be obtained.
In addition, since there is no portion in which the breakdown voltage also deteriorates unevenly in the active region 16, the breakdown voltage is increased and a high voltage operation is possible, so that a larger output power can be obtained.

FIG. 11 is a plan view of another modification of the high-frequency semiconductor device according to one embodiment of the present invention.
FIG. 12 is a cross-sectional view of the high-frequency semiconductor element in the XII-XII cross section of FIG. Note that the cross-sectional view of the high-frequency semiconductor element in the XI-XI cross section of FIG. 11 is the same as FIG.
11 and 12, p-HEMT 74 has basically the same structure as p-HEMT 64, but the differences from p-HEMT 64 are as follows.
That is, the inactive region 52 of the p-HEMT 64 extends on both sides of the gate electrode 18, that is, on both sides of the drain side active region 16a and the source side active region 16b. The source side active region 16b is also divided into two parts. On the other hand, in the p-HEMT 74, the inactive region 52 extends only to the drain side active region 16a, and the drain side active region 16a is divided into the drain side active regions 16a1 and 16a2. The inactive region 52 is not provided in 16b, and the source side active region 16b is not divided.

For this reason, in the p-HEMT 74, since the width of the source side active region 16b is wide, the parasitic resistance Rs between the gate and the source is lowered. Therefore, in the p-HEMT 74, the loss due to the resistance is reduced, and a larger output power can be obtained.
As described above, in the high-frequency semiconductor device according to one embodiment of the present invention, since one side of the drain electrode facing the gate electrode is formed in a concave shape toward the gate electrode, it contacts the drain-side active region. The length of the edge of the drain electrode is longer. Therefore, a larger current can be supplied to the drain side active region. As a result, a high-frequency semiconductor device with high output power can be configured.
In addition, since one side of the drain electrode facing the gate electrode is formed in a concave shape toward the gate electrode corresponding to each of the divided regions of the first region of the active region, it contacts the drain side active region. The length of the edge of the drain electrode is longer. Therefore, a larger current can be supplied to each drain side active region. As a result, a larger current can be supplied to the entire drain-side active region, so that a larger output power can be obtained.
Note that a plurality of p-HEMTs described in the second and third embodiments can be obtained by sharing a source electrode or a drain electrode and arranging gate electrodes with these as symmetry axes like the p-HEMT 46 shown in FIG. The source electrode, the gate electrode, and the drain electrode are continuously disposed, and a high-frequency semiconductor device having a desired output power can be configured.

Embodiment 4 FIG.
FIG. 13 is a plan view of a high-frequency semiconductor device according to one embodiment of the present invention. Note that the cross-sectional view of the high-frequency semiconductor element in the XIII-XIII cross section of FIG. 13 is the same as FIG.
As shown in FIG. 13, the p-HEMT 80 has a circular arc shape in this embodiment, and a semicircular shape in this embodiment. The source-side active region 16 b on the active region 16 with the source electrode 20 as the center. The gate electrode 18, the drain side active region 16a, and the drain electrode 22 are sequentially arranged concentrically toward the outer peripheral side. In the p-HEMT 80, the distance between the gate electrode 18 and the source electrode 20 is made smaller as in the already described p-HEMT, and the distance between the gate electrode 18 and the drain electrode 22 is made smaller than the distance between the gate electrode 18 and the source electrode 20. By increasing the distance Lrd, the gate-drain breakdown voltage Vgd0 is increased while reducing the source resistance.
In the p-HEMT 80, since the drain electrode 22 is located on the outer peripheral side of the gate electrode 18, the drain electrode width (in this embodiment, the circumferential length) is set to the gate width (in this embodiment, (Length in the circumferential direction) is longer in proportion to the radius. That is, the width (the length in the circumferential direction) of the drain side active region 16a is from the electrode width of the gate electrode 18 toward the drain electrode 22 from the gate electrode 18 toward the drain electrode 22, that is, as the drain electrode 22 approaches. The width is continuously expanded. Further, the layer structure of the p-HEMT 80 has the same layer structure as that of the p-HEMT 10. For this reason, it has the same effect as described in the first embodiment.

Further, in the p-HEMT 80, the distance from the gate end to the drain electrode 22 is constant at all positions of the gate width at each position of the drain side active region 16a immediately below the gate. That is, the distance from the gate end to the drain electrode 22 is uniform.
Therefore, a current is uniformly supplied from the drain electrode 22 to the drain side active region 16a, and a maximum operating current proportional to the width of the drain side active region 16a (that is, the length in the circumferential direction) can be obtained. Electric power can be obtained.
Further, the withstand voltage can be increased because there is no portion that deteriorates in the drain side active region 16a, and operation at a higher voltage is possible, so that a larger output power can be obtained.
FIG. 14 is a plan view of a high-frequency semiconductor device according to one embodiment of the present invention.
The p-HEMT 84 shown in FIG. 14 shows an arrangement when a plurality of p-HEMTs 80 are used. In the case of the p-HEMT 84 using a plurality of p-HEMTs 80, it is necessary to connect the electrodes by using wiring such as an air bridge. However, a high frequency semiconductor element having a desired output power is required. Can be configured.
The p-HEMT 80 is a semicircle in this embodiment, but may have any shape as long as it has an arc shape.

As described above, in the high-frequency semiconductor device according to one embodiment of the present invention, the planar shape of the gate electrode and the drain electrode is arranged on the active region in a partial shape of the ring, and the source electrode The gate electrode and the drain electrode are arranged concentrically with the source electrode as the center. With this configuration, the breakdown voltage is high, the maximum operating current can be increased, and the output power is further increased. Can do.
In the above description, the p-HEMT has been described as an example, but the same effect can be obtained in other field effect transistors such as MESFET.

  As described above, the high-frequency semiconductor device according to the present invention is suitable for a power amplifier in a radio communication system such as a satellite communication or a terrestrial microwave line in a high-frequency band of 3 GHz or more.

It is a top view of the high frequency semiconductor device concerning one embodiment of this invention. It is sectional drawing of the high frequency semiconductor element in the II-II cross section of FIG. It is the equivalent circuit of p-HEMT in consideration of pseudo FET of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view which shows the modification of the high frequency semiconductor element which concerns on one embodiment of this invention. It is a top view of the high frequency semiconductor device concerning one embodiment of this invention. It is sectional drawing of the high frequency semiconductor element in the VI-VI cross section of FIG. It is a top view of the modification of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view of the modification of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view of the other modification of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view of the other modification of the high frequency semiconductor device concerning one embodiment of this invention. It is sectional drawing of the high frequency semiconductor element in the XII-XII cross section of FIG. It is a top view of the high frequency semiconductor device concerning one embodiment of this invention. It is a top view of the high frequency semiconductor device concerning one embodiment of this invention.

Explanation of symbols

24 GaAs substrate, 30 channel layer, 16 active region, 18 gate electrode, 20 source electrode, 22 drain electrode, 16a drain side active region, 52 inactive region.

Claims (10)

A semi-insulating semiconductor substrate;
An n-type first electron supply layer, an undoped channel layer, an n-type second electron supply layer, and an undoped Schottky layer are disposed on the semiconductor substrate and sequentially disposed on the semiconductor substrate. An active region;
A gate electrode disposed on the surface of the Schottky layer of the active region;
An undoped cap layer embedded on the surface of the Schottky layer with the legs of the gate electrode buried therein;
And a source electrode and a drain electrode disposed on a surface of the cap layer so as to face each other via the gate electrode,
A first region between the gate electrode and the drain electrode in the active region is disposed wide from the gate electrode toward the drain electrode, and a distance between the gate electrode and the drain electrode is a distance between the gate electrode and the source electrode. A high-frequency semiconductor device characterized by being longer . A semi-insulating semiconductor substrate;
An n-type first electron supply layer, an undoped channel layer, an n-type second electron supply layer, and an undoped Schottky layer are disposed on the semiconductor substrate and sequentially disposed on the semiconductor substrate. An active region;
A gate electrode disposed on the surface of the Schottky layer of the active region;
An undoped cap layer embedded on the surface of the Schottky layer with the legs of the gate electrode buried therein;
A source electrode and a drain electrode disposed on the surface of the cap layer so as to face each other through the gate electrode,
A first region between the gate electrode and the drain electrode in the active region is divided into a plurality through an inactive region adjacent to a part of the gate electrode and extending in the gate length direction of the gate electrode. Rutotomoni divided each regions is arranged wider toward the drain electrode from the gate electrode, high distance between the gate electrode and the drain electrode you characterized by longer than the distance between the gate electrode and the source electrode Frequency semiconductor device.   2. The high frequency semiconductor device according to claim 1, wherein the first region of the active region is continuously wide.   2. The high-frequency semiconductor device according to claim 1, wherein the first region of the active region is disposed so as to be wide in steps.   3. The high frequency semiconductor device according to claim 2, wherein each of the divided regions which are the first regions of the active region is continuously wide.   3. The high-frequency semiconductor device according to claim 2, wherein each of the divided regions which are the first regions of the active region is disposed so as to increase in a stepwise manner.   7. The high-frequency semiconductor device according to claim 1, wherein one side of the drain electrode facing the gate electrode is formed in a concave shape toward the gate electrode.   7. A side of the drain electrode facing the gate electrode is formed in a concave shape toward the gate electrode corresponding to each divided region of the first region of the active region. The high-frequency semiconductor device described.   9. A plurality of source electrodes, gate electrodes, and drain electrodes are continuously disposed by sharing a source electrode or a drain electrode and disposing a gate electrode with these as symmetry axes. The high-frequency semiconductor device according to claim 1. The planar shape of the gate electrode and the drain electrode is arranged on the active region in a partial shape of the ring, and the source electrode, the gate electrode and the drain electrode are concentrically arranged with the source electrode as the center. high-frequency semiconductor device according to any one of claims 1 to 8, characterized in that.

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